The present invention relates to improvements in protectors or guards which can be placed around universal joints, such as the customary Hook's coupling (also known as Cardan joint) in the power take-off of a motor vehicle. The invention also relates to a method of making such protectors.
It is often necessary to utilize the power take-off of a tractor or another heavy-duty vehicle to transmit motion to separable implements, e.g., to rotary hoes, rotary ditchers and/or other agricultural or earth moving implements which are not equipped with discrete prime movers. In many instances, the power take-off is provided with one or more universal joints in order to allow for necessary articulation between the towing or pushing vehicle and the implement which receives motion by way of the power take-off.
The moving parts of the power take-off must be shielded to reduce the likelihood of injury to an operator and/or the likelihood of contamination of moving parts. Such shielding is necessary not only based on normal prudence but is also frequently prescribed by authorities which regulate the manufacture and utilization of such equipment. It is desirable to provide a protector or guard which completely surrounds the moving parts of the power take-off, e.g., a take-off including the engine-driven shaft, a first universal joint which is driven by such shaft, a second shaft which is driven by the first joint, a second universal joint which is driven by the second shaft, and a third shaft which is driven by the second universal joint and transmits torque to the parts of the implement receiving motion from the power take-off.
Heretofore known protectors for the universal joint or joints of a power take-off normally comprise two components which are made of synthetic plastic material and are similar or identical to each other. In many instances, the two components differ only in certain dimensions. One of these components surrounds the first universal joint and a portion of the second shaft, and the other component surrounds the remaining portion of the second shaft and the second universal joint. Each of the two components comprises a tube which surrounds a shaft, a frustoconical section which surrounds one fork of the respective universal joint, and a deformable second tube which spacedly surrounds the remainder of the respective universal joint. Each component further comprises a bearing ring which serves to mount the assembly of the two tubes and frustoconical section on a fork of the universal joint. To this end, a portion of the bearing ring extends into a groove which is machined into the one fork of the corresponding universal joint. Various types of protectors differ from each other in the manner in which the tubes are connected to the frustoconical section and in which the bearing ring is connected to the assembly including the two tubes and the frustoconical section. The mechanical characteristics of each part of the protector should be selected with a view to satisfy the safety regulations in a particular country or in a particular administrative unit of the country. For example, the connections between the tubes and the frustoconical section must stand certain axial stresses which tend to move the respective constituents away from each other. The same applies for the connection between the bearing ring and the corresponding fork of the universal joint. The frustoconical section must withstand (without bending or breaking) certain radially oriented deforming stresses which tend to move its material inwardly toward the adjacent universal joint. On the other hand, the larger-diameter tube must be capable of undergoing at least some deformation in response to contact with the adjacent part or parts of the power take-off, e.g., in response to mutual inclination of two shafts which are coupled to each other by the forks of a universal joint.
In accordance with an earlier proposal of the applicant, the smaller-diameter tube is connected to the corresponding end portion of the frustoconical section by metallic fastening clips which are caused to pass through the material of the tube and through, a collar at the smaller-diameter end of the frustoconical section. The bearing ring of such earlier protector has radially extending tabs received in complementary apertures provided therefor in the tapering part of the frustoconical section. The latter is held against disengagement from the tabs by a further ring which is forcibly applied around the tabs.
A protector which is manufactured by the firm Jean Walterscheid GmbH of Lohmar/Rhineland, German Federal Republic, has a smaller-diameter tube one end of which is formed with an annulus of apertures for radially outwardly extending pins at the smaller-diameter end of the frustoconical section. The tips of the pins form a circle whose diameter matches or approximates the outer diameter of the smaller-diameter tube. Thus, the apertured end of the smaller-diameter tube must be expanded, thereupon forced over the pins and finally pressed inwardly so that the pins penetrate into the apertures and couple the smaller-diameter tube to the smaller-diameter end portion of the frustoconical section. A portion of the bearing ring in the protector which is manufactured by Jean Walterscheid GmbH extends into the circumferential groove of one fork of the respective universal joint and the bearing ring has radial tabs which are received in complementary grooves of the frustoconical section. The frustoconical section and the larger-diameter tube are made of one piece, the same as in accordance with applicant's aforediscussed earlier proposal, so that the rigidity of the frustoconical section matches that of the larger-diameter tube. This is not an ideal solution because the larger-diameter tube is relatively stiff and the rigidity of the frustoconical section is less than satisfactory.
The firm Bondioli & Pavesi of Suzzara, Italy, manufactures a different protector wherein the bearing ring serves to couple the smaller-diameter tube to the respective end portion of the frustoconical section. To this end, the bearing ring surrounds the adjacent end of the smaller-diameter tube and has arms which extend substantially axially of the tubes and carry radially inwardly extending teeth which are received in apertures provided therefor in the respective end portion of the smaller-diameter tube. The arms are outwardly adjacent to the respective end face of the smaller-diameter tube. The bearing ring is further provided with elastic extensions which are inclined with reference to its axis and are received in similarly inclined recesses of the frustoconical section. One end of the larger-diameter tube is forced into the larger-diameter end portion of the frustoconical section.
It is also known to make the frustoconical section and the larger-diameter tube of a single piece of deformable material and to enhance the rigidity of the frustoconical section by a second frustoconical section which is made of a stiff material and is force fit into the deformable frustoconical section.
All of the aforediscussed protectors exhibit a number of serious drawbacks. Thus, the metallic clips which are used in applicant's earlier protector are likely to rust and to thus weaken the connection between the frustoconical section and the smaller-diameter tube. Moreover, the aforementioned further ring contributes to the initial and assembly cost of applicant's earlier protector. Still further, the mechanical properties of the frustoconical section and of the larger-diameter tube are unsatisfactory because the rigidity of the frustoconical section is insufficient and the rigidity of the larger-diameter tube is excessive. This also applies for the protector which is manufactured by Jean Walterscheid GmbH and which exhibits the additional drawback that the connection between the frustoconical section and the smaller-diameter tube is complex and expensive. Still further, the assembly of this protector is a complex procedure because the smaller-diameter tube must be forcibly introduced into the smaller-diameter end portion of the frustoconical section. The protector of Bondioli & Pavesi comprises an excessive number of discrete parts and the cost of reinforcing the frustoconical section is very high.